Protective role of silymarin against manganese-induced nephrotoxicity and oxidative stress in rat

Heavy metals and elderly kidney health: A multidimensional study through Enviro-target Mendelian Randomization

Chronic Kidney Disease (CKD), closely linked to environmental factors, poses a significant public health challenge. This study, based on 529 triple-repeated measures from key national environmental pollution area and multiple gene-related public databases, employs various epidemiological and bioinformatics models to assess the impact of combined heavy metal exposure (Chromium [Cr], Cadmium [Cd], and Lead [Pb]) on early renal injury and CKD in the elderly. Introducing the novel Enviro-Target Mendelian Randomization method, our research explores the causal relationship between metals and CKD. The findings indicate a positive correlation between increased levels of metal and renal injury, with combined exposure caused renal damage more significantly than individual exposure. The study reveals that metals primarily influence CKD development through oxidative stress and metal ion resistance pathways, focusing on three related genes (SOD2, MPO, NQO1) and a transcription factor (NFE2L2). Metals were found to regulate oxidative stress levels in the body by increasing the expression of SOD2, MPO, NQO1, and decreasing NFE2L2, leading to CKD onset. Our research establishes a new causal inference framework linking environmental pollutants-pathways-genes-CKD, assessing the impact and mechanisms of metal exposure on CKD. Future studies with more extensive in vitro evidence and larger population are needed to validate.

Complex interplay of heavy metals and renal injury: New perspectives from longitudinal epidemiological evidence

BACKGROUND

Epidemiological studies have reported associations between heavy metals and renal function. However, longitudinal studies are required to further validate these associations and explore the interactive effects of heavy metals on renal function and their directional influence.

METHOD

This study, conducted in Northeast China from 2016 to 2021, included a four-time repeated measures design involving 384 participants (1536 observations). Urinary concentrations of chromium (Cr), cadmium (Cd), manganese (Mn), and lead (Pb) were measured, along with renal biomarkers including urinary microalbumin (umAlb), urinary albumin-to-creatinine ratio (UACR), N-acetyl-β-D-glucosaminidase (NAG), and β2-microglobulin (β2-MG) levels. Estimated glomerular filtration rate (eGFR) was calculated. A Linear Mixed Effects Model (LME) examined the association between individual metal exposure and renal biomarkers. Subsequently, Quantile g-computation and Bayesian Kernel Machine Regression (BKMR) models assessed the overall effects of heavy metal mixtures. Marginal Effect models examined the directional impact of metal interactions in the BKMR on renal function.

RESULT

Results indicate significant impacts of individual and combined exposures of Cr, Cd, Pb, and Mn on renal biomarkers. Metal interactions in the BKMR model were observed, with synergistic effects of Cd-Cr on NAG, umAlb, UACR; Cd-Pb on NAG, UACR; Pb-Cr on umAlb, UACR, eGFR-MDRD, eGFR-EPI; and an antagonistic effect of Mn-Pb-Cr on UACR.

CONCLUSION

Both individual and combined exposures to heavy metals are associated with renal biomarkers, with significant synergistic interactions leading to renal damage. Our findings elucidate potential interactions among these metals, offering valuable insights into the mechanisms linking multiple metal exposures to renal injury.

Nephroprotective effects of silymarin and its fabricated nanoparticles against aluminum-induced oxidative stress, hyperlipidemia, and genotoxicity

BACKGROUND

Aluminum (Al) is a ubiquitous element with proven nephrotoxicity. Silymarin (SM) is a mixture of polyphenolic components extracted from Silybum marianum and exhibited protective influences. However, SM bioactivity can be enhanced by its incorporation in chitosan (CS) through the use of nanotechnology. This work proposed to assess the protective influence of SM and its loaded chitosan nanoparticles (SM-CS-NPs) on aluminum chloride (AlCl3)-induced nephrotoxicity.

METHODS

Six groups were created randomly from 42 male Wistar rats and each one contains 7 rats (n = 7). Group I, acted as a control and received water. Group II received SM (15 mg/kg/day) and group III administered with SM-CS-NPs (15 mg/kg/day). Group IV received AlCl3 (34 mg/kg) and groups V and VI were treated with SM and SM-CS-NPs with AlCl3 respectively for 30 days.

RESULTS

AlCl3 administration significantly elevated TBARS, H2O2, and kidney function levels besides LDH activity. Whereas GSH, CAT, SOD, GPx, GST, and GR values were all substantially reduced along with protein content, and ALP activity. Additionally, significant alterations in lipid profile, hematological parameters, and renal architecture were observed. Moreover, TNF-α, TGF-β, and MMP9 gene expression were upregulated in kidney tissues. The administration of SM or its nanoparticles followed by AlCl3 intoxication attenuated renal dysfunction replenished the antioxidant system, and downregulated TNF-α, TGF-β, and MMP9 gene expression in renal tissues compared to the AlCl3 group.

CONCLUSION

SM-CS-NPs have more pronounced appreciated protective effects than SM and have the proficiency to balance oxidant/antioxidant systems in addition to their anti-inflammatory effect against AlCl3 toxicity.

Magnetic Resonance Imaging and Manganism: A Narrative Review and Laboratory Recommendations

In recent years, a series of articles has been published concerning magnetic resonance imaging (MRI) studies in a group of patients exposed to manganism, specifically factory workers, welders, and individuals with liver diseases, as well as those abusing home-produced ephedrone. Some potential symptoms of manganese toxicity include motor disturbances, neurocognitive problems, sleep disorders, and psychosocial changes. Despite various publications on MRI research in individuals with an elevated risk of manganism, there is a noticeable absence of a comprehensive review in this field. The detection of the accumulation of manganese in the brain through MRI can confirm the diagnosis and guide appropriate treatment. Due to the high cost of determining manganese ion levels in biological material, an additional aim of the manuscript was to identify simple medical laboratory parameters that, when performed concurrently with MRI, could assist in the diagnosis of manganism. Among these types of parameters are the levels of bilirubin, magnesium, liver enzymes, creatinine, hemoglobin, and hematocrit.

Effects of multiple metals exposure on abnormal liver function: The mediating role of low-density lipoprotein cholesterol

Equilibration of metal metabolism is critical for normal liver function. Most epidemiological studies have only concentrated on the influence of limited metals. However, the single and synergistic impact of multiple-metal exposures on abnormal liver function (ALF) are still unknown. A cross-sectional study involving 1493 Chinese adults residing in Shenzhen was conducted. Plasma concentrations of 13 metals, including essential metals (calcium, copper, cobalt, iron, magnesium, manganese, molybdenum, zinc, and selenium) and toxic metals (aluminum, cadmium, arsenic, and thallium) were detected by the inductively coupled plasma spectrometry (ICP-MS). ALF was ascertained as any observed abnormality from albumin, alanine transaminase, aspartate transaminase, γ-glutamyl transpeptidase, and direct bilirubin. Diverse statistical methods were used to evaluate the single and mixture effect of metals, as well as the dose-response relationships with ALF risk, respectively. Mediation analysis was conducted to evaluate the role of blood lipids in the relation of metal exposure with ALF. The average age of subjects was 59.7 years, and 56.7 % were females. Logistic regression and the least absolute shrinkage and selection operator (LASSO) penalized regression model consistently suggested that increased levels of arsenic, aluminum, manganese, and cadmium were related to elevated risk of ALF; while magnesium and zinc showed protective effects on ALF (all p-trend < 0.05). The grouped weighted quantile sum (GWQS) regression revealed that the WQS index of essential metals and toxic metals showed significantly negative or positive relationship with ALF, respectively. Aluminum, arsenic, cadmium, and manganese showed linear whilst magnesium and zinc showed non-linear dose-response relationships with ALF risk. Mediation analysis showed that LDL-c mediated 4.41 % and 14.74 % of the relationship of plasma cadmium and manganese with ALF, respectively. In summary, plasma aluminum, arsenic, manganese, cadmium, magnesium, and zinc related with ALF, and LDL-c might underlie the pathogenesis of ALF associated with cadmium and manganese exposure. This study may provide critical public health significances in liver injury prevention and scientific evidence for the establishment of environmental standard.

Biochemistry biomarkers and metal levels as indicators of environmental pollution in Danio rerio exposed to the Sorocaba River (S.P.), Brazil

Metal contamination of the environment poses a significant threat to human health and can cause significant damage to aquatic ecosystems. Danio rerio was exposed to Sorocaba River water for 96 h from two different sites in summer (S) and winter (W). Concentrations of Al, Cd, Cu, Mn and Zn were determined in the exposure water and in sediment. At the end of the exposure, the concentrations of Al, Cu and Mn at the Ibiúna point (P1) and Mn at the Itupararanga point (P2) decreased compared to the initial concentrations in the water. In summer and winter, the highest concentrations of Cu and Mn were found in the sediment. Exposure to the Sorocaba River water caused various responses both in summer and winter. For example, GPx decreased in winter, Glutathione S-Transferase (GST) increased in summer, and Nitric Oxide Synthase (NOS) decreased in both seasons in the viscera. In winter, SOD Superoxide Dismutase (SOD) increased, while GPx and GST (winter) decreased in muscle; regarding viscera carbonyl proteins, there was an increase in the summer at P2. Acetylcholinesterase activity decreased in the brain in winter at P2 and NOS decreased in the summer-exposed groups and increased in the winter P2-exposed group. Lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) decreased in viscera (S, P1) and increased in muscle (S, P1 and P2). The glucose and triglycerides increased in muscle, both in summer and winter. Correlation analysis revealed associations between biomarkers from different organs. These alterations suggest that the fish experienced oxidative stress in response to exposure to the Sorocaba River, contaminated with metals, highlighting their vulnerability to environmental pollutants.

Liposomal silymarin anti-oxidative and anti-apoptotic features in lung cells: An implication in cadmium toxicity

BACKGROUND

Several metallic elements with high atomic weight and density are serious systemic toxicants, and their wide environmental distribution increase the risk of their exposure to human. Silymarin (SL), a polyphenol from milk thistle (Silybum marianum) plant has shown protective role against heavy metal toxicity. However, its low aqueous solubility and rapid metabolism limits its therapeutic potential in clinic.

METHODS

We compared the role of silymarin nanoliposomes (SL-L) against cadmium (Cd) toxicity in normal MRC-5 and A 549 cancer cells. MRC-5 and A 549 cells exposed to Cd at 25 and 0.25 µM respectively, were treated with various non-toxic SL-L concentrations (2.5, 5, 10 µM) and cells viability, reactive oxygen species (ROS) generation, apoptosis and levels of cleaved PARP and caspase-3 proteins were determined following incubation.

RESULTS

Results indicated that Cd exposure significantly increased apoptosis due to ROS generation, and showed greater toxicity on cancer cells compared to normal cells. While SL-L at higher concentrations (25 µM and higher) exhibits pro-apoptotic features, lower concentrations (10 and 2.5 µM for MRC-5 and A 549 cancer cells, respectively) played a protective and anti-oxidant role in Cd induced toxicity in both cells. Further, lower SL-L was required to protect cancer cells against Cd toxicity. In general, treatment with SL-L significantly improved cell survival by decreasing ROS levels, cleaved PARP and caspase-3 in both MRC-5 and A 549 cells compared to free silymarin.

CONCLUSION

Results demonstrated that SL-L potential in protecting against Cd-induced toxicity depends on concentration-dependent antioxidant and anti-apoptotic balance.

Exposure to manganese during sertoli cell formation and proliferation disturbs early testicular development in rats

Manganese (Mn) is a metal and important micronutrient. However, exposure to supraphysiological levels of Mn, which occur through fungicides, atmospheric emissions, drainages, and spills, has been related to health risks, including morphometric changes in the male reproductive organs and impairment on gametogenesis and sperm quality, impacting the fertile ability of adult animals. Despite the relevance of the fetal/perinatal period for toxicological studies on Mn, previous data only deal with the physical and neurological development of the offspring, without mentioning their reproductive development. The present study investigated whether exposure to Mn during fetal/perinatal phase, specifically during the period of formation and proliferation of Sertoli cells, impairs the reproductive development of male offspring in early postnatal life. Therefore, pregnant Wistar rats were randomly distributed into 3 experimental groups: Ctl (received saline solution), Mn-9 (received 9 mg/kg of MnCl2), and Mn-90 (received 90 mg/kg of MnCl2). The female rats received the experimental treatment by gavage from gestational day 13 to lactational day 15, i.e., postnatal day (PND) 15 of the pups. Oxidative damage to the genetic material of germ and Sertoli cells, together with a decrease in connexin 43 immunolabeling were observed in the testis of male pups evaluated at PND 15. In addition, an increase in the seminiferous tubules presenting slight epithelium vacuolization and cells with eosinophilic cytoplasm were observed, without apparent epididymal changes. In conclusion, it was demonstrated that Mn perturbed the initial testicular development by altering Sertoli cell integrity through oxidative insult, which may compromise the spermatogenesis in the long-term.

Comparative efficacy of silibinin and nano-silibinin on lead poisoning in Male Wistar rats

Lead (Pb) is an environmental neurotoxin that can lead to toxicity. It has shown that tissues can be exposed to oxidative stress in lead poisoning. Since silymarin is a natural agent with antioxidant effects, this study aimed to investigate the antioxidant and chelation effects of silibinin and nano-silibinin on the oxidative stress status in lead-poisoned rats. Sixty male Wistar rats randomly divided into ten groups (n = 6). Control and Pb groups treated with or without silibinin and nano-silibinin for six days. Following measuring of weight and blood lead levels, biochemical antioxidant parameters evaluated. Finally, a histopathological examination of the liver performed. In this experiment, silibinin and more efficiently nano-silibinin prevented weight loss and blood lead level elevation induced by lead. Also, they increased the attenuated levels of superoxide dismutase (SOD) activity, catalase (CAT), total thiol molecules (TTM), glutathione (GSH), and total antioxidant capacity (TAC). Lead-induced elevation of lipid peroxidation products (MDA) and nitric oxide (NO) normalized to the standard level in silibinin and especially nano-silibinin groups. These data suggested that silibinin and especially nano-silibinin can decrease blood lead levels and prevent weight loss and oxidative stress in the lead-poisoned rat's model.

Clinical relevance of environmental manganese exposure with liver stiffness and steatosis detected by transient elastography in adults

Global manganese pollution to air and water is a significant threat to human health. The associations between manganese and liver stiffness and steatosis have not been reported in epidemiological studies. This study aimed to explore the clinical relevance of blood manganese with liver stiffness and steatosis in adults from the 2017-2018 National Health and Nutrition Examination Survey (N = 4,192). Subjects with excessive alcohol consumption and hepatitis B or C infection were excluded. Liver stiffness and steatosis were detected by transient elastography. Logistic regression and restricted cubic splines were adopted to explore the non-linear dose-response relationships. In multivariate analysis, while higher blood manganese concentrations were not associated with liver stiffness in the total sample and in males, an increased odds of significant liver fibrosis was found with higher blood manganese concentrations (tertile 3 vs. tertile 1) in females [odds ratios (95% confidence intervals): 2.34 (1.32-4.14), P trend < 0.01] and in other races [1.47 (1.05-2.05), P trend = 0.03]. Higher blood manganese concentrations were associated with liver steatosis in the total sample [1.33 (1.04-1.70), P trend = 0.03], in females [1.58 (1.02-2.44), P trend = 0.04], in other races [1.91 (1.50-2.43), P trend < 0.01], and in obese subjects [2.29 (1.13-4.65), P trend = 0.02]. Dose-response analysis showed that the departures from non-linear relationships between blood manganese concentrations and significant liver fibrosis (Pnon-linearity = 0.30) and steatosis (Pnon-linearity = 0.47) were not significant, suggesting that the observed associations were linear. In conclusion, higher blood manganese concentrations were positively associated with liver stiffness and steatosis, and the associations were mainly observed in females, in races other than Non-Hispanic White, and in obese subjects.

PI3K/Akt Signaling Pathway Ameliorates Oxidative Stress-Induced Apoptosis upon Manganese Exposure in PC12 Cells

Manganese (Mn)-induced neurotoxicity has aroused public concerns for many years, but its precise mechanism is still poorly understood. Herein, we report the impacts of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in mediating neurological effects induced by manganese sulfate (MnSO₄) exposure in PC12 cells. In this study, cells were treated with MnSO₄ for 24 h in the absence or presence of LY294002 (a special inhibitor of PI3K). We investigated cell viability and apoptosis signals, as well as levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). The mRNA levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and Caspase-3 were also quantified through real-time quantitative PCR (RT-qPCR); protein levels of serine/threonine protein kinase (Akt) and forkhead box O3A (Foxo3a) were determined by western blot. Increasing of MnSO₄ doses led to decreased SOD, GSH-Px, and CAT activities, while the level of MDA was upregulated. Moreover, cell apoptosis was significantly increased, as the mRNA of Bcl-2 and Caspase-3 was significantly decreased, while Bax mRNA was increased. Phosphorylated Akt (p-Akt) and Foxo3a (p-Foxo3a) were upregulated in a dose-dependent manner. In addition, LY294002 pretreatment reduced the activity of SOD, GSH-Px, and CAT but elevated MDA levels. Meanwhile, LY294002 pretreatment also increased cell apoptosis given the upregulated Bax and Caspase-3 mRNAs and decreased Bcl-2 mRNA. In summary, the PI3K/Akt signaling pathway can be activated by MnSO₄ exposure and mediate MnSO₄-induced neurotoxicity.

D-Ribose-L-Cysteine Improves Glutathione Levels, Neuronal and Mitochondrial Ultrastructural Damage, Caspase-3 and GFAP Expressions Following Manganese-Induced Neurotoxicity

Repeated manganese (Mn) exposure may cause increased production of reactive oxygen species (ROS), with a consequent imbalance in the glutathione (GSH) antioxidant defence system, resulting in cellular dysfunctions, and eventually cell death, particularly in the brain. D-ribose-L-cysteine (RibCys) has been demonstrated to effectively promote the synthesis of glutathione, a potent neutralizer of ROS. In the present study, we examined the effects of RibCys on glutathione levels, apoptotic and astrocytic responses, neuronal ultrastructural integrity, following Mn exposure. Wild-type rats were exposed to either saline, Mn, or/and RibCys for 2 weeks. The Mn-exposed rats received RibCys either as pre-, co-, or post-treatments. Mn caused a marked decrease in GSH levels, overexpression of GFAP and caspase-3, reflecting astrocytosis and apoptosis, and altered ultrastructural integrities of the neuronal nuclei, mitochondria, and myelin sheath of the striatum and motor cortex respectively, while all interventions with RibCys minimized and prevented the neurotoxic events. Our study demonstrates that RibCys effectively attenuates the neurotoxic effects of Mn and may be useful as a therapeutic strategy against neurological consequences of Mn overexposure.

The impact of environmental and occupational exposures of manganese on pulmonary, hepatic, and renal functions

Manganese (Mn) is an essential trace element for humans, but long-term environmental or occupational exposures can lead to numerous health problems. Although many studies have identified an association between Mn exposures and neurological abnormalities, emerging data suggest that occupationally and environmentally relevant levels of Mn may also be linked to multiple organ dysfunction in the general population. In this regard, many experimental and clinical studies provide support for a causal link between Mn exposure and structural and functional changes that are responsible for organ dysfunction in major organs like lung, liver, and kidney. The underlying mechanisms suggested to Mn toxicity include altered activities of the components of intracellular signaling cascades, oxidative stress, apoptosis, affected cell cycle regulation, autophagy, angiogenesis, and an inflammatory response. We further discussed the sources and possible mechanisms of Mn absorption and distribution in different organs. Finally, treatment strategies available for treating Mn toxicity as well as directions for future studies were discussed.

Manganese-induced neurodegenerative diseases and possible therapeutic approaches

INTRODUCTION

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and prion disease represent important public health concerns. Exposure to high levels of  heavy metals such as manganese (Mn) may contribute to their development.

AREAS COVERED

In this critical review, we address the role of Mn in the etiology of neurodegenerative diseases and discuss emerging treatments of Mn overload, such as chelation therapy. In addition, we discuss natural and synthetic compounds under development as prospective therapeutics. Moreover, bioinformatic approaches to identify new potential targets and therapeutic substances to reverse the neurodegenerative diseases are discussed.

EXPERT OPINION

Here, the authors highlight the importance of better understanding the molecular mechanisms of toxicity associated with neurodegenerative diseases, and the role of Mn in these diseases. Additional emphasis should be directed to the discovery of new agents to treat Mn-induced diseases, since present day chelator therapies have limited bioavailability. Furthermore, the authors encourage the scientific community to develop research using libraries of compounds to screen those compounds that show efficacy in regulating brain Mn levels. In addition, bioinformatics may provide novel insight for pathways and clinical treatments associated with Mn-induced neurodegeneration, leading to a new direction in Mn toxicological research.

Health Benefits of Silybum marianum: Phytochemistry, Pharmacology, and Applications

Silybum marianum (SM), a well-known plant used as both a medicine and a food, has been widely used to treat various diseases, especially hepatic diseases. The seeds and fruits of SM contain a flavonolignan complex called silymarin, the active compounds of which include silybin, isosilybin, silychristin, dihydrosilybin, silydianin, and so on. In this review, we thoroughly summarize high-quality publications related to the pharmacological effects and underlying mechanisms of SM. SM has antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, neuroprotective, skin-protective, antidiabetic, and other effects. Importantly, SM also counteracts the toxicities of antibiotics, metals, and pesticides. The diverse pharmacological activities of SM provide scientific evidence supporting its use in both humans and animals. Multiple signaling pathways associated with oxidative stress and inflammation are the common molecular targets of SM. Moreover, the flavonolignans of SM are potential agonists of PPARγ and ABCA1, PTP1B inhibitors, and metal chelators. At the end of the review, the potential and perspectives of SM are discussed, and these insights are expected to facilitate the application of SM and the discovery and development of new drugs. We conclude that SM is an interesting dietary medicine for health enhancement and drug discovery and warrants further investigation.

Silymarin protects the structure of kidney in the neonatal rats exposed to maternal cadmium toxicity: A stereological study

The present study aimed to investigate the protective effect of silymarin on maternal cadmium toxicity complications in the kidney of neonatal rats. Forty adults Wistar female rats were selected and placed with male rats for copulation. The pregnant animals were randomly divided into five groups (n = 8) including control, sham, silymarin, cadmium, and silymarin + cadmium. The animals received 400 mg L^-1 cadmium and 100 mg kg^-1 silymarin (sub-cutaneously, three days per week, three weeks). Two-day neonates were dissected and their right kidneys were fixed in 10.00% buffered formalin solution and processed by standard paraffin embedding. Tissue sections were stained by hematoxylin and eosin and analyzed histologically and stereologically. The data were statistically analyzed by SPSS using a one-way ANOVA test and Tukey's post-hoc. The results showed that silymarin significantly increased the neonatal rats' weight compared to the control group. Cadmium significantly decreased the weight of neonatal rats' kidneys. The results of histological studies indicated that cadmium caused subacute glomerulosclerosis, severe damage to urinary tubules such as tubular necrosis, and severe hyperemia in the medulla, but silymarin could preserve these complications. Stereological results revealed that cadmium decreased the total volume of kidney, medulla, and proximal and distal tubules and increased interstitial tissue and indicated the protective effects of silymarin on maternal cadmium toxicity complications in the kidney tissue of neonatal rats. It can be concluded that the administration of silymarin during pregnancy may be used as a useful and effective way of protecting the maternal cadmium toxicity complications in the kidney tissue of neonatal rats.

Milk thistle (Silybum Marianum) as an antidote or a protective agent against natural or chemical toxicities: a review

Biological and chemical agents cause dangerous effects on human health via different exposing ways. Recently, herbal medicine is considered as a biological and safe treatment for toxicities. Silybum marianum (milk thistle), belongs to the Asteraceae family, possesses different effects such as hepatoprotective, cardioprotective, neuroprotective, anti-inflammatory and anti-carcinogenic activities. Several studies have demonstrated that this plant has protective properties against toxic agents. Herein, the protective effects of S. marianum and its main component, silymarin, which is the mixture of flavonolignans including silibinin, silydianin and silychristin acts against different biological (mycotoxins, snake venoms, and bacterial toxins) and chemical (metals, fluoride, pesticides, cardiotoxic, neurotoxic, hepatotoxic, and nephrotoxic agents) poisons have been summarized. This review reveals that main protective effects of milk thistle and its components are attributed to radical scavenging, anti-oxidative, chelating, anti-apoptotic properties, and regulating the inflammatory responses.

Gallic acid and omega-3 fatty acids decrease inflammatory and oxidative stress in manganese-treated rats

IMPACT STATEMENT

Humans and animals are regularly exposed to toxic chemicals with subsequent adverse effects. Manganese exposure occurs via contaminated sources; over-exposure is associated with neuronal, hepatorenal dysfunction, etc. This work advances the field of natural chemopreventive agents by reporting evidence lacking in the literature on GA and ω-3-FA obtained primarily from the diet in protecting biological beings against toxic chemicals. Individually, GA and ω-3-FA exhibit various pharmacological effects. Our findings confirm the previous reports; however, we demonstrate the additional evidence for GA and ω-3-FA in abating toxic response incumbent on oxidative damage associated with manganese exposure. These findings further underscore the relevance of GA usage in food, cosmetics-pharmaceutical industries, and ω-3-FA as a safe supplement. Dietary supplements with GA and fish oil-rich in ω-3FA may be the potential natural therapy against hepatorenal injury in individuals inadvertently or occupationally exposed to manganese, thereby, promoting human and veterinary health outcomes.

Hematobiochemical Disturbances and Oxidative Stress After Subacute Manganese Chloride Exposure and Potential Protective Effects of Ebselen in Rats

The present study aimed to detect the possible disturbances induced by subacute exposure to manganese chloride (MnCl₂) on some biomarkers of hematology, clinical chemistry and oxidative stress, serum iron homeostasis, and ferritin status beside the histopathological alterations in hepatic and renal tissues, and the potential protective effects of ebselen on the Mn toxicity were also evaluated. Forty-eight rats were divided into four groups: Group 1 was used as a control. Groups 2, 3, and 4 were administered of ebselen as a single protective dose (15 mg/kg BW) intraperitoneal, daily manganese chloride (50 mg/kg BW) orally, and ebselen plus manganese chloride, respectively. The administrations were conducted for 30 days. Blood and tissue samples were collected at the end of the treatment for various experimental tests. Results revealed that MnCl₂ did not significantly change in erythrogram with leukocytosis and neutrophilia but significantly increased serum aminotransferases and alkaline phosphatase activities, bilirubin (total, direct, and indirect), globulins, triglycerides, total cholesterol, creatinine, urea, manganese, iron and ferritin concentrations and hepatic glutathione, renal malondialdehyde and nitric oxide levels and hepatic superoxide dismutase activity, while serum albumin, hepatic malondialdehyde, and nitric oxide concentrations were significantly decreased besides non-statistical change in serum total proteins concentration. Ebselen has reduced the disturbances in these analytes in combined treatment group. Collectively, subacute exposure to MnCl₂ causes disturbance in the leukogram, and hepatic and renal functions with marked renal oxidative stress. It also disturbed serum iron homeostasis and ferritin status. Remarkably, ebselen appears to be highly effective in attenuating the various adverse effects of manganese.

Could male reproductive system be the main target of subchronic exposure to manganese in adult animals?

Manganese (Mn) is one of the most common chemical elements on Earth and an essential micronutrient in animal organism. However, in supraphysiological levels and long-term exposures, it is a potential toxicant. Although nervous system is the most studied in relation to Mn toxicity, other tissues can have their function impaired by Mn in high doses. The present study investigated the possible adverse effects of subchronic exposure to supraphysiologic level of Mn (5 mg/kg or 15 mg/kg, intraperitoneally) on reproductive, neurobehavioral, renal and hepatic parameters of male rats. For the first time, the vulnerability of these parameters to Mn was concomitantly investigated. While our results demonstrate that Mn treatments were not sufficient to produce a marked effect of neurotoxic, hepatotoxic or renal toxicity in adult rats, we found typical indicators of reproductive toxicity such as histopathological changes (major in testes and epididymis) and impaired sperm concentration and quality. Mn, under these experimental conditions, seems to exert reproductive toxicity by different testicular mechanisms, i.e. direct and indirect action on germ cells. On the other hand, exposure to Mn did not change the pattern of cognitive and emotional behaviors and the histological organization of kidneys of experimental rats. The liver showed a weight increasement and hidropic degeneration, probable due to the detoxification overload. In summary, for the first time it was demonstrated that adult male reproductive system was more sensitive to Mn toxicity than nervous, hepatic and renal systems, although nervous system is known as the main target tissue of this metal.

Acacia hydaspica ethyl acetate extract protects against cisplatin-induced DNA damage, oxidative stress and testicular injuries in adult male rats

Background

Cisplatin (CP), an effective anticancer agent, carries the risk of impairing testicular function leading to infertility. The present study aimed at evaluating the protective effect of A. hydaspica ethyl acetate extract (AHE) against CP-induced oxidative stress and testicular injuries in rats.

Methods

Rats were divided into six groups (n = 6). Group I (control), group II (CP single dose on day 16). Group III received AHE for 21 days. Group IV (CP + AHE; post- treatment group). Group V (AHE + CP; pre-treatment group) and group VI (CP + Sily).

Results

CP treatment reduced serum testosterone (T), LH and FSH, decreased the activity level of antioxidant enzymes while increased the concentration of oxidative stress markers, i.e. thiobarbituric acid reactive substances (TBARS), H₂O₂ and nitric oxide (NO) along with corresponding DNA damages. Furthermore, CP induced adverse morphological changes in testis of rats including reduced epithelial height and tubular diameter, increased luminal diameter with impaired spermatogenesis. Pre and post-treatment with AHE reduced the side effects of CP in testis tissues through improvement in the reproductive hormonal secretions, enzymatic activities, histological and DNA damage parameters. Pretreatment seems to be more effective and equivalent to silymarin group in reversing the CP deleterious effects as compared to post-treatment.

Conclusion

The results demonstrated that A. hydaspica treatment in CP-induced testicular toxicity augments the antioxidants defense mechanism, reverted the level of fertility hormones, suppressed the histomorphological alterations and DNA damages and thus provides the evidence that it may have a therapeutic role in free radical mediated diseases.

Possible protective role of silybin against polymyxin E-induced toxic effect in rat kidneys: A biochemical approach

AIMS

Polymyxin E was used for treating gram-negative bacterial infections but not recently for fear of its nephrotoxicity. Silybin has potential to counteract nephrotoxicity; however, few studies have investigated its protective effect on the kidney in an animal model. The purpose of the present study was to assess whether silybin could decrease elevated urine and serum renal biochemical markers induced by polymyxin E in rat kidney.

METHODS

Forty rats were divided randomly into four groups of 10 rats: control (I), vehicle (II), treatment (III, using polymyxin E), and protection (IV, using silybin and polymyxin E). Urine was collected daily for 7 days to test for N-acetyl-beta-D-glucosaminidase (NAG). Serum was collected after euthanizing the rats on day 7 to test kidney functions. RESULTS Group III had significant increases in NAG (all P < 0.001) compared with the other groups, but no differences were found between the other groups. Significant differences in kidney functions were found between Group III and Groups I and II, and between Group IV and Groups I and II (all P < 0.001). No differences were found between Groups III and IV.

CONCLUSIONS

Group III results suggested an affection of the renal glomeruli and tubules, and Group IV results suggested a possible protective effect of silybin against polymyxin E-induced nephrotoxicity. Additional studies are recommended that use different doses of silybin for Groups III and IV to test for statistical differences for kidney functions and that test the protective effect of silybin against nephrotoxicity induced by polymyxin E in humans.

Redox dynamics of manganese as a mitochondrial life-death switch

Sten Orrenius, M.D., Ph.D., pioneered many areas of cellular and molecular toxicology and made seminal contributions to our knowledge of oxidative stress and glutathione (GSH) metabolism, organellar functions and Ca+2-dependent mechanisms of cell death, and mechanisms of apoptosis. On the occasion of his 80th birthday, we summarize current knowledge on redox biology of manganese (Mn) and its role in mechanisms of cell death. Mn is found in all organisms and has critical roles in cell survival and death mechanisms by regulating Mn-containing enzymes such as manganese superoxide dismutase (SOD2) or affecting expression and activity of caspases. Occupational exposures to Mn cause "manganism", a Parkinson's disease-like condition of neurotoxicity, and experimental studies show that Mn exposure leads to accumulation of Mn in the brain, especially in mitochondria, and neuronal cell death occurs with features of an apoptotic mechanism. Interesting questions are why a ubiquitous metal that is essential for mitochondrial function would accumulate to excessive levels, cause increased H2O2 production and lead to cell death. Is this due to the interactions of Mn with other essential metals, such as iron, or with toxic metals, such as cadmium? Why is the Mn loading in the human brain so variable, and why is there such a narrow window between dietary adequacy and toxicity? Are non-neuronal tissues similarly vulnerable to insufficiency and excess, yet not characterized? We conclude that Mn is an important component of the redox interface between an organism and its environment and warrants detailed studies to understand the role of Mn as a mitochondrial life-death switch.

"Manganese-induced neurotoxicity: a review of its behavioral consequences and neuroprotective strategies"

Manganese (Mn) is an essential heavy metal. However, Mn’s nutritional aspects are paralleled by its role as a neurotoxicant upon excessive exposure. In this review, we covered recent advances in identifying mechanisms of Mn uptake and its molecular actions in the brain as well as promising neuroprotective strategies. The authors focused on reporting findings regarding Mn transport mechanisms, Mn effects on cholinergic system, behavioral alterations induced by Mn exposure and studies of neuroprotective strategies against Mn intoxication. We report that exposure to Mn may arise from environmental sources, occupational settings, food, total parenteral nutrition (TPN), methcathinone drug abuse or even genetic factors, such as mutation in the transporter SLC30A10. Accumulation of Mn occurs mainly in the basal ganglia and leads to a syndrome called manganism, whose symptoms of cognitive dysfunction and motor impairment resemble Parkinson’s disease (PD). Various neurotransmitter systems may be impaired due to Mn, especially dopaminergic, but also cholinergic and GABAergic. Several proteins have been identified to transport Mn, including divalent metal tranporter-1 (DMT-1), SLC30A10, transferrin and ferroportin and allow its accumulation in the central nervous system. Parallel to identification of Mn neurotoxic properties, neuroprotective strategies have been reported, and these include endogenous antioxidants (for instance, vitamin E), plant extracts (complex mixtures containing polyphenols and non-characterized components), iron chelating agents, precursors of glutathione (GSH), and synthetic compounds that can experimentally afford protection against Mn-induced neurotoxicity.

Does silybin protect against toxicity induced by polymyxin E in rat kidney?

AIMS

Although once a common antibiotic, polymyxin E fell out of favor after reports of its nephrotoxicity. However, recent concerns with gram-negative bacteria, which are resistant to multiple antibiotics, have resulted in increased interest in polymyxin E. Silybin is a known antihepatotoxic drug and may have potential for protecting the kidney from polymyxin E. Therefore, the aim of the current study was to evaluate whether silybin affected the damages produced by polymyxin E on the rat kidney.

METHODS

Four groups of rats with 10 rats per group were included in the study: control (no treatment, group I), vehicle (control vehicle treatment, group II), polymyxin E treatment (group III), and polymyxin E and silybin treatment (group IV). Groups II-IV received intravenous treatment twice a day for 7 days. All rats were euthanized after 7 days. Histological, ultrastructural, and morphometric analyses were performed on the rats' kidney tissues.

RESULTS

Analysis of tissues from group III showed differences from groups I and II, such as glomerular and tubular affection and changes in morphometric measures. Results for group IV were more similar to those of groups I and II than those of group III.

CONCLUSIONS

Our results suggested that administering silybin with polymyxin E alleviated polymyxin E-induced nephrotoxicity in the rat kidney. Future biochemical studies should investigate whether silybin could ameliorate the nephrotoxicity caused by polymyxin E in rats and whether concomitant administration of silybin could be an effective clinical pharmacological strategy to protect against polymyxin E-induced insult in human kidneys.

Silymarin alleviates hepatic oxidative stress and protects against metabolic disorders in high-fat diet-fed mice

Silymarin is a potent antioxidant medicine and has been widely used for the treatment of liver diseases over 30 years. Recent studies suggest that silymarin may benefit patients with glucose intolerance. However, the mechanism underlying the action of silymarin is not clarified. The aim of this work was to assess the impact of silymarin on glucose intolerance in high-fat diet (HFD)-fed mice, and explore the potential therapeutic mechanisms. C57BL/6 mice were fed with HFD for 12 weeks, randomized, and treated orally with vehicle saline or silymarin (30 mg/kg) daily for 30 days. We found that silymarin significantly improved HFD-induced body weight gain, glucose intolerance, and insulin resistance in mice. Silymarin treatment reduced HFD-increased oxidative stress indicators (reactive oxygen species, lipid peroxidation, protein oxidation) and restored HFD-down-regulated activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) in the plasma and/or liver of the HFD-fed mice. Furthermore, silymarin decreased HFD-up-regulated hepatic NADPH oxidase expression and NF-κB activation in mice. Additionally, silymarin treatment mitigated HFD-increased plasma IL-1β, TNF-α levels, and HFD-enhanced hepatic NO, TLR4, and iNOS expression in mice. These novel data indicate that silymarin has potent anti-diabetic actions through alleviating oxidative stress and inflammatory response, partially by inhibiting hepatic NADPH oxidase expression and the NF-κB signaling.

Silymarin as a Natural Antioxidant: An Overview of the Current Evidence and Perspectives

Silymarin (SM), an extract from the Silybum marianum (milk thistle) plant containing various flavonolignans (with silybin being the major one), has received a tremendous amount of attention over the last decade as a herbal remedy for liver treatment. In many cases, the antioxidant properties of SM are considered to be responsible for its protective actions. Possible antioxidant mechanisms of SM are evaluated in this review. (1) Direct scavenging free radicals and chelating free Fe and Cu are mainly effective in the gut. (2) Preventing free radical formation by inhibiting specific ROS-producing enzymes, or improving an integrity of mitochondria in stress conditions, are of great importance. (3) Maintaining an optimal redox balance in the cell by activating a range of antioxidant enzymes and non-enzymatic antioxidants, mainly via Nrf2 activation is probably the main driving force of antioxidant (AO)  action of SM. (4) Decreasing inflammatory responses by inhibiting NF-κB pathways is an emerging mechanism of SM protective effects in liver toxicity and various liver diseases. (5) Activating vitagenes, responsible for synthesis of protective molecules, including heat shock proteins (HSPs), thioredoxin and sirtuins and providing additional protection in stress conditions deserves more attention. (6) Affecting the microenvironment of the gut, including SM-bacteria interactions, awaits future investigations. (7) In animal nutrition and disease prevention strategy, SM alone, or in combination with other hepatho-active compounds (carnitine, betaine, vitamin B₁₂, etc.), might have similar hepatoprotective effects as described in human nutrition.

Effects of silymarin on methotrexate-induced nephrotoxicity in rats

Methotrexate (MTX) is widely used in the treatment of various malignancies and nononcological diseases but its use has been limited by its nephrotoxicity. Silymarin (SLY), a natural flavonoid, has been reported to have antioxidant, anti-inflammatory and anti-apoptotic effects. This study was carried out to determine whether SLY exerts a protective effect against MTX-induced nephrotoxicity. Rats were divided into six groups: Group 1 (saline, i.p., single injection), Group 2 (0.5% carboxymethyl cellulose (CMC), by gavage once daily for five consecutive days), Group 3 (SLY, 300 mg/kg per day, i.p. for five consecutive days), Group 4 (MTX, 20 mg/kg, i.p., single injection), Group 5 (MTX + CMC similarly as groups 2 and 4) and Group 6 (MTX + CMC + SLY similarly as groups 2, 3 and 4). Histopathologic alterations including apoptotic changes of the kidney were evaluated. MTX injection exhibited dilated Bowman's space, inflammatory cell infiltration, glomerular and peritubular vascular congestion and swelling of renal tubular epithelium cells. Apoptotic cell death was also markedly increased in renal tubules after MTX administration. SLY treatment resulted in statistically significant amelioration in the histological alterations and reduced the number of TUNEL-positive cells as compared with the MTX treated rats (p < 0.05). In conclusion, SLY treatment leads to a reduction on MTX-induced renal damage in rats. Since SLY is safe and acceptable for human consumption, further studies to define the exact mechanism of the protecting effect of SLY on MTX-induced nephrotoxicity and the optimum dosage of this compound would be useful.